Metabolic disorders represent a major public health burden nowadays. From these metabolic disorders, obesity and diabetes mellitus (DM) may be considered the most significant ones. Obesity is characterized by an excess of body fat, where body mass index (BMI) is used for its classification. When an individual has a BMI between 25 and 30 kg/m2 is considered overweight, while a BMI over 30 kg/m2 classifies an individual as obese. This excessive fat is very harmful and may even reduce life expectancy. On the other hand, DM encompasses a cluster of disorders characterized by chronic hyperglycemia that are a result of defects in insulin action, insulin secretion, or both. The exponential increase of these metabolic disorders is, in part, due to erroneous dietary habits that lead to an inadequate intake of essential nutrients. Moreover, while the prevalence of metabolic diseases increases, the fertility trends decrease, illustrating an association that may, or may not, be direct. In fact, there is an increasing number of children, adolescent and men in reproductive age suffering from metabolic disorders. It is well known that the occurrence of a normal spermatogenesis is dependent on the metabolic cooperation established between testicular cells, particularly concerning glucose metabolism and insulin signaling. Therefore, it is crucial to unveil these mechanisms in individuals with metabolic disorders, how they are affected by the disease and how they change the fertility of males. In recent years, several studies have provided new information concerning alterations induced by metabolic disorders in male reproductive health. In addition, it was highlighted that testicular cells possess several mechanisms that react to hormonal fluctuations to counteract hyper- and hypoglycemic events. In this chapter, we will discuss the effects of DM and obesity in the regulation of testicular insulin signaling and glucose metabolism as well as the importance of an adequate diet and how these events are implicated in the reproductive health of males.